2006 Cobalt, purchased used with 27,000, now at 49,000. Soon after purchase during a hot July, the check engine light came on, Power Steering on the display screen and the trans would jerk until reached 35 mph, or so. After disconnecting the TCM and/or battery over a few weeks, the problem disappeared until the next hot July in 2010. Again cleared up as mysteriously as before. Then in December, reoccurred, power steering issue was worse, and it would not clear as easily or stay cleared. Decided to first try replacing the power steering motor under recall. It made the problem worse. Dealer replaced the TCM because that's what the codes told them to do. Fixed nothing. Car came with a side post battery, which I replaced myself this last winter with another side post (Autozone insisted it should be a top post)/what does that little grey tube do?. Dealer says this is not standard and may be causing the problem, but can't tell me how. But could it be? They apparently didn't notice this during the $300 TCM job. In the meantime the problem disappears for 1-2 weeks at a time after first going 1-2 days with the "little lock warning light/power steering warning" activating, then those warnings and the check engine light, then the check engine light only (which clears the trans and steering issues) then the check engine light disappears on its own. I have read hours of threads on this and other sites and consumer blogs. The dealer claims/feigns ignorance on any of this ("we've never encountered this before"). And I've finally began to notice that when these other problems occur, I have a power/voltage fluctuation - the lights dim and brighten, the fan slows and speeds, the A/C cuts in and out. I'm not anxious to drop another $300 plus to the dealer to replace the BCM since they are just guessing. My question is has anyone ever come up with the cause/solution? I see lots of complaints, but no solution. My fear is that the complainers stop complaining after the problem is fixed, or if they get rid of the car, but they don't report back.